Placental measurements associated with intelligence quotient at age 7 years.

We hypothesized that placental villous branching that is measured by disk chorionic plate expansion and disk thickness is correlated with factors also involved in regulation of branching growth of other fetal viscera (e.g. lung, kidney) including neuronal dendrites, and thus may be associated with variation in childhood intelligence quotient (IQ). IQ at age 7 years was assessed using the Wechsler Intelligence Scale for Children. Placental measures [placental weight (g), thickness (mm), chorionic plate surface diameters (cm), area (cm2), shape, and cord length and cord eccentricity] were independent variables in regression analyses of age 7-year IQ in 12,926 singleton term live born infants with complete placental data. Analyses were stratified on gender with adjustment for socioeconomic status, race, parity, gestational age, exact age at testing and centered parental ages. After adjustment for covariates, placental measurements were independently associated with IQ at age 7 years but results varied by gender. Chorionic plate diameters were only associated with higher IQ in girls. Placental thickness was positively associated with higher IQ for boys and girls. We have previously shown that placental measures affect age 7-year body mass index and diastolic blood pressure. Here we demonstrate that specific measures, placental chorionic plate diameters in girls and disk thickness, independent of gender, are correlated with age 7-year IQ. Further exploration of the possible interaction of these factors on the placental villous arborization reflected by the chorionic plate expansion and placental thickness that correlate with age 7-year IQ, as well as other age 7 somatic features as previously addressed, is indicated.